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How do we solve length word problems using addition and subtraction?
Goal:
Goal:
Think About It!
Goal: Identify how to write a math sentence to solve a length word problem.
Madelyn has a black skateboard that is 28 in long. She has a red skateboard that is 40 in long. Madelyn needs to add 3 in to the length of each of her skateboards to use them in the competition. How long will each skateboard be after it is fixed?
Madelyn with a black skateboard measuring 28 inches long and a red skate board measuring 40 inches long.
We can use the lengths in the problem to help Madelyn find out! A length is the distance from one end of an object to the other. We measure length using rulers with units of measurement like inches and centimeters. We can use unit words or abbreviations to show the units we are measuring. When we want to solve a length word problem, we need to use the lengths in the same units to find the answer!
Click each box to see the problem-solving steps for word problems!
Step 1
1. Read the problem.
Step 2
2. Look for important information.
Step 3
3. Write a math sentence.
Step 4
4. Choose a way to solve.
Step 5
5. Solve and label your answer.
After we read the problem and find the important information, we need to write a math sentence. We will add or subtract lengths to solve each word problem. For some length word problems, we need to write more than one math sentence. This is because we are comparing the lengths of two different items to another length! Look at this word problem below:
Logan is 45 inches tall. Ava is 38 inches tall. They want to ride a roller coaster but need to be 50 inches tall to ride. How many more inches tall do Logan and Ava need to be in order to ride the roller coaster? The sentence How many more inches tall do Logan and Ava need to be in order to ride the roller coaster? is underlined.
This problem looks at a different type of length known as height. Height is how tall or short something is. We know how tall Logan is, and we know how tall Ava is. We know they both need to be a certain height, but they are not quite tall enough. The question is asking us to compare Logan’s height to the height required for the roller coaster AND Ava’s height to the height required for the roller coaster. That means we will need two math sentences, one for Logan and one for Ava!
Click each tab to see how to solve Logan and Ava’s word problem!
Read the problem
Logan is 45 inches tall. Ava is 38 inches tall. They want to ride a roller coaster but need to be 50 inches tall to ride. How many more inches tall do Logan and Ava need to be in order to ride the roller coaster? The sentence How many more inches tall do Logan and Ava need to be in order to ride the roller coaster? is underlined.
It helps to read the problem as many times as you need to! Try to imagine the problem in your head to help you understand it.
Find the important information
Logan is 45 inches tall. Ava is 38 inches tall. They want to ride a roller coaster but need to be 50 inches tall to ride. How many more inches tall do Logan and Ava need to be in order to ride the roller coaster? 45 and 38 are highlighted in red. 50 is highlighted in blue. How many more is circled in red. The sentence How many more inches tall do Logan and Ava need to be in order to ride the roller coaster? is underlined.
The important information is any numbers or key words and the question. 45, 38, and 50 are the important numbers. The word “inches” tells you this is a length problem. The words “How many more” tell you that you will need to subtract lengths. The question is the last sentence. It asks how much taller each child needs to be to ride the roller coaster.
Write and solve the first math sentence.
Logan is 45 inches tall. Ava is 38 inches tall. They want to ride a roller coaster but need to be 50 inches tall to ride. How many more inches tall do Logan and Ava need to be in order to ride the roller coaster? 45 and 38 are highlighted in red. 50 is highlighted in blue. How many more is circled in red. The sentence How many more inches tall do Logan and Ava need to be in order to ride the roller coaster? is underlined.
\({50 - 45 = 5}\) We start by subtracting 5 from 0. To do this we must borrow from the tens place \({5 - 1 = 4}\). We then add 10 to zero to get 10. Now we can subtract \({10 - 5 = 5}\) Now we can minus the tens place \({4 - 4 = 0}\)This leaves us with 0 in the tens place making the answer 5.
Start with the first child in the problem, Logan. He is 45 inches tall. He needs to be 50 inches tall to ride the roller coaster. We know we need to subtract. We will subtract 45 from 50! 50 minus 45 equals 5!
Write and solve the second math sentence.
Logan is 45 inches tall. Ava is 38 inches tall. They want to ride a roller coaster but need to be 50 inches tall to ride. How many more inches tall do Logan and Ava need to be in order to ride the roller coaster? 45 and 38 are highlighted in red. 50 is highlighted in blue. How many more is circled in red. The sentence How many more inches tall do Logan and Ava need to be in order to ride the roller coaster? is underlined.
\({50 - 45 = 5}\) We start by subtracting 5 from 0. To do this we must borrow from the tens place \({5 - 1 = 4}\). We then add 10 to zero to get 10. Now we can subtract \({10 - 5 = 5}\) Now we can minus the tens place \({4 - 4 = 0}\)This leaves us with 0 in the tens place making the answer 5.
\({50 - 38 = 12}\) We start by subtracting 8 from 0. To do this we must borrow from the tens place \({5 - 1 = 4}\). We then add 10 to zero to get 10. Now we can subtract \({10 - 8 = 2}\) Now we can minus the tens place \({4 - 3 = 1}\)This leaves us with 1 in the tens place making the answer 12.
Now we can move on to what we know about Ava. She is 38 inches tall. She needs to be 50 inches tall to ride the roller coaster. We know we need to subtract. We will subtract 38 from 50! 50 minus 38 equals 12!
Label each answer.
Logan is 45 inches tall. Ava is 38 inches tall. They want to ride a roller coaster but need to be 50 inches tall to ride. How many more inches tall do Logan and Ava need to be in order to ride the roller coaster? 45 and 38 are highlighted in red. 50 is highlighted in blue. How many more is circled in red. The sentence How many more inches tall do Logan and Ava need to be in order to ride the roller coaster? is underlined.
\({50 - 45 = 5}\) We start by subtracting 5 from 0. To do this we must borrow from the tens place \({5 - 1 = 4}\). We then add 10 to zero to get 10. Now we can subtract \({10 - 5 = 5}\) Now we can minus the tens place \({4 - 4 = 0}\)This leaves us with 0 in the tens place making the answer 5.
Logan needs to be
5 inches taller.
\({50 - 38 = 12}\) We start by subtracting 8 from 0. To do this we must borrow from the tens place \({5 - 1 = 4}\). We then add 10 to zero to get 10. Now we can subtract \({10 - 8 = 2}\) Now we can minus the tens place \({4 - 3 = 1}\)This leaves us with 1 in the tens place making the answer 12.
Ava needs to be
12 inches taller.
We will label the answers we found to answer the question. How many more inches do Logan and Ava need to be in order to ride the roller coaster?
Logan needs to be 5 inches taller. Ava needs to be 12 inches taller.
Let’s use what we have learned to solve Madelyn’s word problem!
Madelyn has a black skateboard that is 28 in long. She has a red skateboard that is 40 in long. Madelyn needs to add 3 in to the length of each of her skateboards to use them in the competition. How long will each skateboard be after it is fixed? The sentence How long will each skateboard be after it is fixed? is underlined.
After we read the problem, we need to find the important information.
Question
What are the important numbers?
28, 40, and 3 are the important numbers.
Question
What is the key word?
The word “add” is the key word.
Question
What is the question?
The question is the last sentence in the problem. It asks how long each skateboard will be after it is fixed.
Madelyn has a black skateboard that is 28 in long. She has a red skateboard that is 40 in long. Madelyn needs to add 3 in to the length of each of her skateboards to use them in the competition. 28 is highlighted in red , and 40 is highlighted in red. Add is circled, 3 is highlighted in yellow. How long will each skateboard be after it is fixed? The sentence How long will each skateboard be after it is fixed? is underlined.
We know that 28, 40, and 3 are the important numbers. The key word “add” tells us that we need to add to answer the question. Madelyn needs to add 3 in to each of her skateboards if she wants to use them in the competition. Let's write an addition sentence for the black skateboard. Click the Show Me button to see!
\({28 + 3 = ?}\)
Madelyn has a black skateboard that is 28 in long. She has a red skateboard that is 40 in long. Madelyn needs to add 3 in to the length of each of her skateboards to use them in the competition. 28 is highlighted in red , and 40 is highlighted in red. Add is circled, 3 is highlighted in yellow. How long will each skateboard be after it is fixed? The sentence How long will each skateboard be after it is fixed? is underlined.
\({28 + 3 = ?}\)
Let’s solve the math sentence. You can write a vertical addition sentence if it is easier for you to add that way! Click the Show Me button to see the sum of 28 plus 3!
\({28 + 3 = 31}\)
Madelyn has a black skateboard that is 28 in long. She has a red skateboard that is 40 in long. Madelyn needs to add 3 in to the length of each of her skateboards to use them in the competition. 28 is highlighted in red , and 40 is highlighted in red. Add is circled, 3 is highlighted in yellow. How long will each skateboard be after it is fixed? The sentence How long will each skateboard be after it is fixed? is underlined.
\({28 + 3 = 31}\)
We wrote and solved the first addition sentence for the black skateboard. Now we need to write an addition sentence for the red skateboard! Remember, Madelyn needs to add 3 in to the red skateboard too! Click the Show Me button to see the addition sentence!
\({40 + 3 = ?}\)
Madelyn has a black skateboard that is 28 in long. She has a red skateboard that is 40 in long. Madelyn needs to add 3 in to the length of each of her skateboards to use them in the competition. 28 is highlighted in red , and 40 is highlighted in red. Add is circled, 3 is highlighted in yellow. How long will each skateboard be after it is fixed? The sentence How long will each skateboard be after it is fixed? is underlined.
\({28 + 3 = 31}\)
\({40 + 3 = ?}\)
Let’s solve the second math sentence. You can write a vertical addition sentence if it is easier for you to add that way! Click the Show Me button to see the sum of 40 plus 3!
\({40 + 3 = 43}\)
Madelyn has a black skateboard that is 28 in long. She has a red skateboard that is 40 in long. Madelyn needs to add 3 in to the length of each of her skateboards to use them in the competition. 28 is highlighted in red , and 40 is highlighted in red. Add is circled, 3 is highlighted in yellow. How long will each skateboard be after it is fixed? The sentence How long will each skateboard be after it is fixed? is underlined.
\({28 + 3 = 31}\)
\({40 + 3 = 43}\)
We solved both math sentences! That means we have the length of each skateboard after it is fixed. To answer the question, each number needs a label word. It will be a unit word or abbreviation because we are solving a length word problem.
Question
How long will each skateboard be after it is fixed?
The black skateboard will be 31 in long. The red skateboard will be 43 in long.
You can write math sentences to help solve a length word problem using addition or subtraction!